Chainpoint

Chainpoint is an open standard for creating a timestamp proof of any data, file, or process.

Anchor an unlimited amount of data to the Bitcoin blockchain. Verify the integrity and existence of data without relying on a trusted third-party.

...plus hundreds of others use Chainpoint.

How does Chainpoint work?

Chainpoint links a hash of your data to a blockchain and returns a timestamp proof. A Chainpoint Node receives hashes which are aggregated together using a Merkle tree. The root of this tree is published in a Bitcoin transaction. The final Chainpoint proof defines a set of operations that cryptographically link your data to the Bitcoin blockchain.

What is a Chainpoint Proof?

A Chainpoint proof contains the information to verify that the hash of some data is anchored to a blockchain. It proves the data existed at time it was anchored. Chainpoint proofs can be verified without reliance on a trusted third party.

Chainpoint Node API

Chainpoint Nodes have an HTTP API. You can interact with Nodes using any programming language that supports HTTP calls. Thousands of Chainpoint Nodes operate as part of a global network.

Chainpoint Node API Tutorial

Chainpoint JS Client

This Chainpoint javascript client can be used in both Browser and Node.js based Javascript applications using callback functions, Promises (using .then, .catch), or Promises (using async/await) functional styles.

Chainpoint JS Client

Chainpoint Proof Versions

The third major version of the Chainpoint proof specification is currently in testing and scheduled for release soon. A JSON schema validator is available.

Name	Description
@context string, required	the JSON-LD context for the proof
type string, required	the JSON-LD type definition
hash string, required	hash value between 40 and 128 hex characters. Must be even length.
hash_id_node string, required	a Version 1 UUID with embedded timestamp and 5 byte BLAKE2s hash of the input data. Timestamp represents Node server time (UTC) of hash submission.
hash_submitted_node_at string, required	Human readable ISO 8601 timestamp extracted from time embedded in the hash_id_node
hash_id_core string, required	a Version 1 UUID with embedded timestamp and 5 byte BLAKE2s hash of the input data. Timestamp represents Core server time (UTC) of hash submission.
hash_submitted_core_at string, required	Human readable ISO 8601 timestamp extracted from time embedded in the hash_id_core
branches - an array of branch objects. Branches can be nested without limit and MUST be traversed only after executing 'ops'. (required only at root)
label string, optional	text string representing the branch name
ops array, optional	an array of operations objects. Operations are performed in sequence to arrive at an intermediate hash prior to entering a nested branch.
branches array, optional	nested array of branch objects. Each branch contains ops; labels and additional nested branches are optional.
ops - an array of operation objects (required under every 'branches' object)
lstring, optional	left concatenate a value. If the value is a hexadecimal string, it will be read as a hexadecimal byte array, otherwise the string will be converted to its byte value assuming UTF-8 encoding.
rstring, optional	right concatenate a value. If the value is a hexadecimal string, it will be read as a hexadecimal byte array, otherwise the string will be converted to its byte value assuming UTF-8 encoding.
op string, optional	an operation to perform on the current value combined with a previous 'l' or 'r' operation. Current operations: 'sha-224', 'sha-256', 'sha-384', 'sha-512', 'sha3-224', 'sha3-256', 'sha3-384', 'sha3-512', or the special purpose 'sha-256-x2' which applies 'sha-256' twice.
anchors - an array of anchor objects (required under every 'ops' object).
type string, required	one of 'cal' (Calendar), 'btc' (Bitcoin), 'tcal' (Testnet Calendar), 'tbtc' (Testnet Bitcoin), or 'eth' (Ethereum) anchor types
anchor_id string, required	an identifier used to look up embedded anchor data. e.g. a Bitcoin transaction or block ID.
uris array, optional	an array of special purpose string URI's, each of which can be used to lookup and retrieve the exact hash resource required to validate this anchor. The URI MUST return only a Hexadecimal hash value as a string. The URI MUST also contain the 'anchor_id' value to lookup the URI resource. This strict requirement is to allow automated clients to retrieve and validate intermediate hashes when verifying a proof. The body value returned by the URI MUST be of even length and match the regex [a-fA-F0-9].

Example

{
  "@context": "https://w3id.org/chainpoint/v3",
  "type": "Chainpoint",
  "hash": "ffff27222fe366d0b8988b7312c6ba60ee422418d92b62cdcb71fe2991ee7391",
  "hash_id_node": "66a34bd0-f4e7-11e7-a52b-016a36a9d789",
  "hash_submitted_node_at": "2018-01-09T02:47:15Z",
  "hash_id_core": "66bd6380-f4e7-11e7-895d-0176dc2220aa",
  "hash_submitted_core_at": "2018-01-09T02:47:15Z",
  "branches": [
    {
      "label": "cal_anchor_branch",
      "ops": [
        {
          "l": "node_id:66a34bd0-f4e7-11e7-a52b-016a36a9d789"
        },
        {
          "op": "sha-256"
        },
        {
          "l": "core_id:66bd6380-f4e7-11e7-895d-0176dc2220aa"
        },
        {
          "op": "sha-256"
        },
        {
          "l": "nist:1515465960:1041862e0f3987dca3aab3a91767d2a2ebbf251451b740879adb0926f0ee325e608d5c311e3f64a002dc5266337efc34ebdbf0032c7a253a8fbb64c1b0fb625f"
        },
        {
          "op": "sha-256"
        },
        {
          "r": "725a969557e64600aa2bbe50e75fc12dd913620144660836441a97f6d36babf9"
        },
        {
          "op": "sha-256"
        },
        {
          "l": "f21aac3945aee46d0cd888faff3364cc7640f88c9bdfefb1072a4bb82c6702b6"
        },
        {
          "op": "sha-256"
        },
        {
          "r": "c59058f17b93b609f4b49366c8808099a715836b6c08b45a1dc6ac762820ae27"
        },
        {
          "op": "sha-256"
        },
        {
          "l": "985635:1515466042:1:https://a.chainpoint.org:cal:985635"
        },
        {
          "r": "0e20cff025777bec277cd3a0599eaf5efbeb1ea7adf5ec5a39126a77fa57f837"
        },
        {
          "op": "sha-256"
        },
        {
          "anchors": [
            {
              "type": "cal",
              "anchor_id": "985635",
              "uris": [
                "https://a.chainpoint.org/calendar/985635/hash"
              ]
            }
          ]
        }
      ],
      "branches": [
        {
          "label": "btc_anchor_branch",
          "ops": [
            {
              "l": "0e20cff025777bec277cd3a0599eaf5efbeb1ea7adf5ec5a39126a77fa57f837"
            },
            {
              "op": "sha-256"
            },
            {
              "r": "9d7e8027c869d7446db8f2a5f371d967f5ba9d3a88f1703a1674f57963d3448d"
            },
            {
              "op": "sha-256"
            },
            {
              "l": "28c6aa4416d1b0aa474bc52fd32175ec7d15980772874617b5000aff043ac6cb"
            },
            {
              "op": "sha-256"
            },
            {
              "r": "4c297218f2015d4f84a6561ca06c1c28b2f6cca1500315ef6d4944ad6822b974"
            },
            {
              "op": "sha-256"
            },
            {
              "r": "f6a15401357e6e177583dbf5aa82b5ed5ae1043d1bda3faba88ca0fdb90e01c0"
            },
            {
              "op": "sha-256"
            },
            {
              "r": "ae9137386a03fdcdb9a1554a6e4fcd9697efed17caaa0221ce35e12bfc9fbf2d"
            },
            {
              "op": "sha-256"
            },
            {
              "l": "fa5643778470a9175644affe35e0177a13b2446d73182be0963d53b1d09214ab"
            },
            {
              "op": "sha-256"
            },
            {
              "l": "01000000013d9bfb8c553b3a7c9c030ea9b0f47c7e4c457e47a1ad2d9c751c8eb0e02fee70010000006a47304402201eac07288c3881f354564bb9da0d8267174cdc9e8c42ca82c2129a0416c806220220104e9932a89259472c84be7722f77324efa43a65ca79dd5bb8b6aab0ac9788000121032695ca0d3c0f7f8082a6ef66e7127e48d4eb99bef86be99432b897c485962fa8ffffffff020000000000000000226a20"
            },
            {
              "r": "ca694202000000001976a9149f1f4038857beedd34cc5ba9f26ac7a20c04d51988ac00000000"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "aa7008cdf722a674cc3532727ee39e9ebc810fb047cc7f4edc302705fcee3985"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "f0fae6f1dc00b678596e230584430b95bad9c1439f03293250b5a9bfb993b500"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "a79b18abcde7db6554e95c14ed544231f59670318033fc6e2e28142341ef223a"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "12105db21e488b1d8eb44fbce8bc5e3fcb7becc35fe4d9d30696ef7baff853eb"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "0ce1848d74ea8705858e468e045e7891f2b5f9c8ed37eeaa00be51846460294e"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "52af6b21e7b370f680e984b8a1e34ffdb45770d3cf599357ce245bad8c820d50"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "bb5bd9669a3bc3202e460091185f8103863da4263f417e85479fc3bb40a882d1"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "25bb84e8a36904224182b28adb04956d1251d4312b4e975c4ee3ff74a50bce1d"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "l": "a55b52dc8079febc3a8b673ee123829c176aca7dabb330299afdeac2bfea16d6"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "r": "3bf18e7d4ffaab9988d14b1402fe9817ea6c50fa626dd78bcaba18a9b16184f1"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "r": "af9ae1010333cf6e5ea124e5827a8bf0f40f68ab9a5bf283f93f744046b07a5d"
            },
            {
              "op": "sha-256-x2"
            },
            {
              "anchors": [
                {
                  "type": "btc",
                  "anchor_id": "503275",
                  "uris": [
                    "https://a.chainpoint.org/calendar/985814/data"
                  ]
                }
              ]
            }
          ]
        }
      ]
    }
  ]
}

Name	Description
@context	the JSON-LD context for the receipt
type	receipt type definition specifying hash method and version
targetHash	hash value being anchored to the blockchain
merkleRoot	merkle tree root value that is anchored to the blockchain
proof	merkle proof establishing link from the targetHash to the merkleRoot
anchors
type	anchor type definition specifying anchoring method
sourceId	identifier, such as a transaction id, used to locate anchored data

Example

{
  "@context": "https://w3id.org/chainpoint/v2",
  "type": "ChainpointSHA256v2",
  "targetHash": "bdf8c9bdf076d6aff0292a1c9448691d2ae283f2ce41b045355e2c8cb8e85ef2",
  "merkleRoot": "51296468ea48ddbcc546abb85b935c73058fd8acdb0b953da6aa1ae966581a7a",
  "proof": [
    {
      "left": "bdf8c9bdf076d6aff0292a1c9448691d2ae283f2ce41b045355e2c8cb8e85ef2"
    },
    {
      "left": "cb0dbbedb5ec5363e39be9fc43f56f321e1572cfcf304d26fc67cb6ea2e49faf"
    },
    {
      "right": "cb0dbbedb5ec5363e39be9fc43f56f321e1572cfcf304d26fc67cb6ea2e49faf"
    }
  ],
  "anchors": [
    {
      "type": "BTCOpReturn",
      "sourceId": "f3be82fe1b5d8f18e009cb9a491781289d2e01678311fe2b2e4e84381aafadee"
    }
  ]
}

Receipt Types

Receipt type values indicate the hash type and version of the receipt. The following values are supported.

Type	Description
ChainpointSHA224v2	Chainpoint 2.0 receipt using SHA-224
ChainpointSHA256v2	Chainpoint 2.0 receipt using SHA-256
ChainpointSHA384v2	Chainpoint 2.0 receipt using SHA-384
ChainpointSHA512v2	Chainpoint 2.0 receipt using SHA-512
ChainpointSHA3-224v2	Chainpoint 2.0 receipt using SHA3-224
ChainpointSHA3-256v2	Chainpoint 2.0 receipt using SHA3-256
ChainpointSHA3-384v2	Chainpoint 2.0 receipt using SHA3-384
ChainpointSHA3-512v2	Chainpoint 2.0 receipt using SHA3-512

Anchor Types

Anchor type values indicate the method and location of the anchored data. The following values are supported. Support for additional methods is planned.

Type	Description
BTCOpReturn	Anchored to a Bitcoin transaction within an OP_RETURN output.
ETHData	Anchored to an Ethereum transaction within the data field.

Name	Description
Header
chainpoint_version	version of the Chainpoint standard
hash_type	hashing algorithm used to encrypt target data (sha256)
merkle_root	root of the Merkle Tree that is published in the blockchain
tx_id	blockchain transaction id
timestamp	nonauthoritative Unix timestamp of the target
Target
target_hash	hash of the target that is being recorded in the blockchain
target_proof	Merkle proof used to prove target_hash is part of Merkle tree
target_URI (optional)	path to the target
Extra
custom (optional)	array of user defined key value pairs

Example

{
  "header": {
    "chainpoint_version": "1.1",
    "hash_type": "SHA-256",
    "merkle_root": "8dbd52c5ff89b70711b06c143520ef4eb295c51040757c7a4ab56303f0f6b68f",
    "tx_id": "77d93bce0f0ff76f1a52424f9c0aeb165990dc37a5e3aaf85031a2f6ab2967d1",
    "timestamp": 1438317621
  },
  "target": {
    "target_hash": "a64f10ca86a880115cc271232dc8577606dc6223cf009a4dd1290cd55b2d6a28",
    "target_uri ": "https://www.someurl.com/target/id",
    "target_proof": [
      {
        "parent": "ee32ac6eb702c289ba2a932e6562b2c45070121cacb26cabdee433a6cf2086cd",
        "left": "a64f10ca86a880115cc271232dc8577606dc6223cf009a4dd1290cd55b2d6a28",
        "right": "f07934733450ba14972b8fbea4c39ac05b0b8e2d8a45ddde9dbe03bb70942b6a"
      },
      {
        "parent": "8dbd52c5ff89b70711b06c143520ef4eb295c51040757c7a4ab56303f0f6b68f",
        "left": "ee32ac6eb702c289ba2a932e6562b2c45070121cacb26cabdee433a6cf2086cd",
        "right": "07084efda9cf5488ef9d4f9ad8bca8521581aaa32331b62aeb2fe3e132e62d1a"
      }
    ]
  },
  "extra": [
    {
      "custom_key_1": "value_1"
    },
    {
      "custom_key_2": "value_2"
    }
  ]
}

Verifying Chainpoint Proofs

Verification confirms that the proof is well formatted, and all proof operations lead to the expected anchor hash on the blockchain. Verification of version 3.x proofs can be performed with the Chainpoint CLI. Verification of older versions can be performed using the chainpoint-validate Javascript package for Node.js.